Observation of Nonlinear Self-Trapping in Momentum Space Bose-Einstein Condensates*

Self-trapping is a phenomenon intrinsically linked to the nonlinear nature of Bose-Einstein Condensates (BECs), arising from interatomic interactions. Going beyond the single-particle picture, self-trapping has significant implications for band structures, phase transition dynamics, quantum metrology, and more.

This talk explores research on self-trapping in a spin-orbit coupled BEC that is complemented by a stationary optical lattice. Despite the repulsive interatomic interactions in our system, the momentum-space realization leads to an effectively attractive behavior observed in our experiments. We create a Raman-induced spin-orbit coupled BEC and combine it with a stationary optical lattice to control momentum state tunneling between two spin-orbit band minima. Utilizing targeted Raman detuning ramping protocols, we measure atomic current flow between the system's eigenstates. In the self-trapping regime, the current flow is damped, and the state mixtures can become fixed at specific ratios.

This work demonstrates an intriguing new experimental platform for detailed studies of this important nonlinear phenomenon.